In the control of drug abuse, and in many other police activities, there is frequently a need for a bag to contain an exhibit, in such a way that it will become self-evident if the exhibit has been tampered with in any way. This is particularly desirable where the exhibit is required for evidential purposes.
This requirement has been recognised for a considerable period of time, but although bags are produced with barbed-type closures, nevertheless tampering is still possible and the main object of this invention is to provide improvements whereby a bag can be produced economically and yet give substantial security against tampering with the contents, unless such tampering becomes self-evident.